1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer and the like, and more particularly, it relates to an apparatus having fixing means for fixing an unfixed toner image to a recording material.
2. Related Background Art
There have been proposed various methods and apparatuses for obtaining an image by using an electrophotography. For example, as disclosed in Japanese Patent Application Laid-Open No. 61-100770, there is a method in which latent images corresponding to the number of color decomposition of an original image are formed on a photosensitive drum as an image forming member and then are developed to form toner images, and, after a multicolor image is formed on a transfer drum by successively transferring the toner images thereon after every development, the multicolor image is transferred onto a recording material, thereby obtaining a color copy.
Further, for example, as disclosed in Japanese Patent Application Laid-Open No. 61-149972, there is a method in which latent images corresponding to the number of color decomposition of an original image are formed on a photosensitive drum as an image forming member and then are developed to form toner images, and the toner images are transferred onto a recording material after every development, thereby obtaining a multi-color copy.
Further, there is a method in which formation of latent images corresponding to the number of color decomposition of an original image on a photosensitive drum and development with color toners are repeated and, after color toner images are superimposed, they are transferred onto a recording material collectively, thereby obtaining a color image.
In a multicolor image forming apparatus in which the color image is obtained by superimposing, a thickness of the toner layer (color image) on the recording material is greater than a thickness of a toner layer (monochromatic image) obtained by a monochromatic image forming apparatus by two or three times, and, thus, the heat capacity of the entire toner layer becomes great, with the result that a difference in fixing ability between usage of a normal paper and usage of a recording material such as a thick paper having great heat capacity becomes noticeable.
Accordingly, when the image is formed on the thick paper, a line speed is decreased to increase a fixing nip time (refer to Japanese Patent Application Laid-Open Nos. 60-80885 and 60-86574).
With such an arrangement, the heat amount itself given to the toner layer is increased, thereby eliminating the difference in fixing ability.
In the above-mentioned conventional techniques, in case of the thick paper, since the line speed is decreased during the image formation, although the fixing ability can be maintained, through-put (the number of copies formed per unit time) is worsened.
An object of the present invention is to provide an image forming apparatus in which a good image can be formed even on a thick recording through-out.
Another object of the present invention is to provide an image forming apparatus comprising unfixed toner image forming means for forming an unfixed toner image on a recording material, and fixing means for fixing the unfixed toner image formed by the unfixed toner image forming means onto the recording material, and wherein a toner amount of the unfixed toner image forming means is smaller than a toner amount of the unfixed toner image formed on a second recording material having a thickness smaller than that of the first recording material by the unfixed toner image forming means.
The other objects and features of the present invention will be apparent from the following detailed explanation referring to the accompanying drawings.